hey guys! I’ve searched and search and old trans leaks I can find on the site is from the front pump seal. This leak is different and it’s pissing trans fluid like crazy in reverse and at idle in park.

Just for history. 6 months ago I had to reseal a leak between trans and transfer case and this doesn’t seem to be far enough back. The leak is coming from right at the back of the trans and it’s spitting it into the front driveshaft coming from the transfer case making a big mess. Source seems to be right above the rear of the trans pan so it looks like it’s coming from the rear of the pan. I drove 400 miles mostly downhill to San Diego. Once I got there I could hear a u Joint squeek and what felt like the double ujoints at the front of the rear driveshaft binding a bit. Mechanic inspected there and said it isn’t the ujoints(I think he was wrong). Feeling the vibration and hearing the squeek I decided to drive it back uphill 400 miles home to have it looked at by my regular guy tomorrow. Stop for pizza for the kids and in the 3-4 minutes the truck was idling I lost probably 1.5 quarts of atf. Babied it home retracing my driving through the parking lot to see no leaks at the stop sign where I pulled in and it wasn’t leaking when I stopped for gas 80 miles before. Babied it home and no leaking. Started it up 20 minutes later with no leaking. Threw it in reverse and after about 2 feet of moving it spewed another quart.

I live in a pretty remote city where people hate trans work. Any suggestions on where to start with the leak or what may cause it?

i know I’ll get asked....
no trans temp sensor
fluid was a little dark but didn’t smell burnt
no metal shavings in the fluid

 

Obviously the cause of your leak is different, but my 04 Navi w/4R100 leaked fluid out the top vent hole/tube when I got it a little, maybe a lot hot pulling an enclosed trailer. Fluid running down the back of the trans from the top of the main case.

 

You say you leak seems to be rear of the pan, check around the flywheel inspection plate just to be sure, mt 4R100 blew out that seal last year after towing my boat home. would only leak when under pressure once it was put into a drive gear, my trans was 10 years old at that point and had an older style pump seal more prone to leaking. If you're E brake is strong enough, set it, chock the wheels, put the vehicle in a drive gear, and look underneath to see if you can spot the leak.

 

Similar thing happened to me this summer. Driving back to NJ from a camping trip outside of DC. Started blowing smoke from under the Ex. Turned out the front seal was dripping oil on the exhaust right under the torque converter housing whenever the heat and pressure went up. I would imagine that towing 11000 Lb in 95+ heat would do it with a bad seal.

The original seal was just plain neoprene rubber and will harden over time. The new seals are Viton and will probably never leak again.

I replaced the seal in my garage on a lazy Saturday.

 

Yeah, this one for sure isn’t the front pump and there is no possible way that is an option. It is somewhere right by the t-case. Front of the trans is dry and isn’t doing it under load. At idle in park.

 

In my opinion without seeing it it's coming out of the top vent. You either have too much fluid it it or the check valve on the right side of the transmission between the inlet and outlet has gone into bypass. Two coolers is not a good idea on this transmission. If the cooling line reaches a certain back pressure restriction the check-valve bypasses the cooling and only circulates the fluid within the transmission itself. This is to prevent catastrophic failure and gives you time to pull over and get off the road.

Also from what I understand these transmissions do not cool while in reverse. That's why they have a tendency to spew fluid on a hot day pushing a heavy trailer uphill in reverse.

Good luck!

 

FordxFour, the OP has updated his rig to exactly what Ford did to all the EXs after the first year or so, a cooling loop inside the radiator tank then into an air to oil cooler in front of the radiator. Ford seems to think that those two coolers are OK and most trucks running around and towing do just fine with that setup.
I do agree that adding additional coolers in addition to these can lead to unwanted amounts of back pressure, but I think the setup the OP is running isn't the source of the problem he is having.

 

My 04Navi has the 4R100 Trans. Factory, it has no external air trans cooler, just the line that runs through the radiator. I added a medium duty external in front of the radiator and have had no issues. My GlowShift Trans temp gauge has me around 140 w/o tow and around 185 when towing. Did not have the gauge before I installed the cooler so I can not say if, and how much temps have changed. Not sure what you mean about not cooling when in reverse? Front pump is always making pressure, always sending fluid through the cooler lines whenever the engine is running. Reverse changes the gears so the output shaft spins in the opposite direction while in 1st gear. Cooling will not be as good as when you are moving forward, but the engine fan is still pulling air, and thus cooling whatever is up there. I agree running in reverse pushing a trailer will make the trans get hot, but it should not be much difference as when you do the same low speed going forward. How far are you pushing that trailer in reverse up hill?

 

Leaking front seals on 4R100s are a recurring topic here, typically involves reversing a heavy trailer uphill. The 4X4 rigs have the advantage of using 4LOW to help reduce the heat generated (I regularly use 4LOW when backing my big TT) during backing. Here is a recent thread discussing the situation including comment from Mark K about the causes. https://www.ford-trucks.com/forums/1...l-trailer.html

 

Maybe I should have said inadequate cooling(earlier models)due to lack of factory install. Not the circulation of the fluid itself. As I mentioned, I'm just guessing here without seeing it. LOL...that's why shops don't give prices over the phone...

If it is coming out of the vent, it's either too hot or overfilled.

 

My error, I thought the OP said it was leaking from the back of the trans, not the front seal. Unsubscribed so as not to inject useless jabber.

 

Not to hijack the thread, but I have a '00 v10 rwd and I just recently put in a new radiator. The old one had no oil cooler ports but I have an external trans cooler.

With the new one in I just have the oil cooling ports plugged up. From what I'm reading on that thread, is it best to use both the factory external cooler WITH the radiator oil cooler? If so how do I add lines to hook tranny fluid lines up to the radiator?

 

Why wouldn't you use the rad. Should also be of help in cold climates for keeping the temps from getting too cold.

 

Yeah, that's going to draw a sharp rebuke from Mark K.

 

It has always only had an external cooler and I don't tow all that much, so I figured I wouldn't mess with the lines and connect it to the radiator. But reading about this issue, I wonder if I should go ahead and get it hooked up to the radiator. Just to clarify, it is supposed to be connected to both the radiator and external cooler? How should I add lines to connect it to the radiator?